Lawyers remain divided on the merits of the Government's proposed citizenship changes, as Immigration Minister Peter Dutton introduced the legislation for the contentious measures into Parliament this morning.

A key plank of the legislation is the power to strip citizenship from dual nationals if they fight with "a listed terrorist organisation overseas".

Any dual citizen who is "convicted of a specific terrorism related offence" or engages in "specified terrorist related conduct" would also cease to be Australian.

The changes relate to sections of the Citizenship Act which are "self-executing", rather than requiring a decision by the minister — a suggestion which had earlier triggered rowdy opposition from some Cabinet ministers.

The minister has confirmed there will be an avenue for judicial appeal in the legislation.

Speaking in Parliament this morning, Mr Dutton said allegiance was a "duty owed by all citizens to their sovereign state" and was recognised in the Citizenship Act.

"The High Court has found that an alien is a person who does not owe allegiance to Australia," he said.

"By acting in a manner contrary to their allegiance, the person has chosen to step outside of the formal Australian community."

He said the bill proposed three mechanisms for "automatic loss of citizenship".

The mechanisms include two new provisions for loss of citizenship if a person acts "inconsistently with their allegiance to Australia by engaging in certain terrorist conduct" or is convicted of a specified terrorism offence by an Australian court.

The legislation also proposes an extension of the provision for a person fighting in the armed forces of another country against Australia.

Constitutional lawyer Professor Greg Craven said a person's citizenship could lapse or self-cancel if they fell under a certain category.

"There's no action by a minister, there's no action by the executive Government of the Commonwealth, and that's important because it means that you're not having an executive officer exercising judicial power," Professor Craven said.

"If your citizenship did lapse in that way, and you presented yourself in Australia, you would be perfectly free to say, 'No, that's not the case, I didn't do it, I wasn't there, I wasn't a member of that body', and ultimately that would have to be determined by a court."

Professor Craven said opening the matter up for a court appeal could counter concern the process could be abused.

"It's a fundamental distinction, because in Australian law only judicial officers can exercise judicial power," Professor Craven said.

He said the appeal process made it less likely the bill would face a constitutional challenge.

But the legislation does not sit well with all in the legal sector — particularly the notion of the automatic application of provisions.

Mr Dutton has said senior public servants, advised by Government lawyers, will play a role in deciding whether a dual national accused of terrorism has met the criteria to be stripped of their citizenship.

Greg Barns from the Australian Lawyers Alliance said: "On who's evidence are we going to rely? It's unlikely to work, it's certainly unfair, and it's unnecessary".

"There's no doubt there are still constitutional problems with this bill, and that's one of them.

"It is not the executive in our system of governance to assume the role of the judiciary, and that's what it looks like."

Labor indicates support for changes

The Federal Opposition says it supports updating the citizenship act to automatically strip citizenship from Australian terrorists with another nationality.

"We support the updating of that, and we do so on the basis it doesn't render people stateless," Labor's immigration spokesman Richard Marles said this morning.

"We obviously want to see what legislation actually appears later this morning, but Labor will be working in a bipartisan way in a constructive way with the Government to affect a sensible update to the Citizenship Act."

But Labor is cooler on the idea of the law applying retrospectively, saying the Parliamentary Joint Committee on Intelligence and Security needs to examine it.

"It's not an idea that we would normally support ... but we'll look at what the proposal actually contains today and the appropriate place for that to now go is the committee and we'll work through that issue on the committee.

"It is a question that needs to be examined carefully by the committee."

Possibility for retrospective application

In announcing the legislation yesterday, Prime Minister Tony Abbott said there was a possibility the bill could be altered to apply retrospectively.

That would mean dual citizens currently serving sentences for terrorist related offences could be deported after leaving jail, as well as preventing the 120 Australians believed to be currently fighting overseas from returning.

The bill will be considered by Parliament's Intelligence and Security Committee, chaired by Liberal MP Dan Tehan.

"We have a history of being thorough in what we do, we have now considered three major pieces of national security legislation as a committee," Mr Tehan said.

"I would believe that what we will be doing again this time is considering this legislation in detail, and making recommendations again where we see, we think that legislation needs to be improved.

"This is the type of thing where we'll have to look at the available evidence, where we'll have to look [at] the legal views with regard to retrospectivity.

"It's not something which is done as a matter of course...but I think this will be a matter that the committee will give deep and considered thought to."

Professor Craven said amending the legislation to make it retrospective was not a foregone conclusion.

"Retrospectivity is always a challenge, and it's always one of those things conservative governments traditionally are very reluctant to do," Professor Craven said.

"Those people who have been dealt with for terrorism-related offences have been dealt with by the courts," Mr Barns pointed out.

He said many such people had already served a punishment for their offences, and it would be unfair to impose another.

Outspoken senator Cory Bernardi will support proposal

While the debate within the Coalition over citizenship was playing out, Liberal Senator Cory Bernardi raised concerns the Government was heading in a dangerous direction.

Senator Bernardi now says he is comfortable with the current proposal and will support it in the Senate.

"In creating any legislative change there is always going to be different points of view and they need to be accommodated," Senator Bernardi said.

"Usually they're accommodated through the Cabinet process and then it goes to the party room.

"Of course I regret that Cabinet deliberations had to be played out in the public domain but ultimately it's outcomes that are the most important."

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